A new species of Xiphinema americanum group (Nematoda: Longidoridae) from Iran, with additional data on three known species.

One new and three known species of the genus Xiphinema from the rhizosphere of fruit trees and rose shrubs in East Azarbaijan province, Iran, are presented based on the morphological, morphometric and molecular characters. The new species is distinguished by its 2.0-2.1 mm long body, relatively flattened lip region with 8.7-10.0 µm width, set off from body contour by a deep constriction, odontostyle 82.5-88.0 µm long, V = 52-54, reproductive system didelphic-amphidelphic with symbiotic bacteria in the reflexed ovaries, tail conoid, dorsally convex with rounded to slightly subdigitate tip (42.0-43.5 µm long, c = 61-65, c' = 1.6-1.8), and males unknown. The new species, X. babaii sp. n., looks very close to X. californicum, and is regarded as its cryptic species, being separated from it using some morphological differences. Their separation was further corroborated using molecular data. Three known species belonging to the Xiphinema americanum group namely X. primum, X. pachtaicum and X. simile were also collected during present study, and new data were provided for them. Xiphinema simile is a new record for the Iran's nematode fauna. Molecular phylogenetic studies using partial sequences of 28S rRNA gene D2-D3 fragments were performed, and the phylogenetic relationships of the new species were discussed.